Atokura Nappe

Atokura Nappe Fujimoto et al., 1953

Thrust nappe composed of Permian - Paleocene geological bodies overlies Sanbagawa Metamorphic Rocks.

Type locality: Atokura, Aokura, Shimonita city, Kanra county, Gunma prefecture
Thrust nappe
Deposition (Amphibolite): Early Cretaceous (105 Ma, K-Ar)
Deposition (Gneiss): Early Cretaceous (110 Ma, K-Ar)
Deposition (Tonalite): Early Cretaceous (112 Ma, K-Ar)
Thrust: Palecene - middle Miocene (ca. 60 - 16 Ma)
Correlation: Kurosegawa Belt?

Metamorphic facies (Greenrock mélange): Pumpellyite-Actinolite
Lithofacies (Amphibolite): Garnet amphibolite, Biotite garnet gneiss, Tonalite
Lithofacies: Chert, Mylonitic aplite granite
Lithofacies (Greenrock mélange): Actinolite rocks, Amphibolite, Alkaline amphibolite

Upper limit: Unconformity (Matsuyama Group)
Lower limit: Atokura Thrust fault (Sanbagawa Metarmophic Rocks) = Pre-Cretaceous Median Tectonic Line

Atokura Nappe (Saitama pref.)
[ Upper ]
/--/--/--/--/-
Yorii Welded Tuff, Paleocene
/--/--/--/--/-
Yorii Formation, Late Cretaceous - Paleocene
/--/--/--/--/-
Atokura Formation, Cretaceous
/--/--/--/--/-
Kinshozan Quartz Diorite, Permian
/--/--/--/--/-
[ Lower ]

Atokura Nappe (Gunma pref.)
[ Upper ]
/--/--/--/--/-
Kotsutateyama Tuff, Paleocene
/--/--/--/--/-
Atokura Formation, Cretaceous
/--/--/--/--/-
Yotsumatayama Quartz Diorite, Early Cretaceous
/--/--/--/--/-
Kawaiyama Quartz Diorite, Permian
/--/--/--/--/-
[ Lower ]

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

Distribution: Atokura, Aokura, Shimonita city, Kanra county, Gunma pref.; Kanezawa, Minano city, Chichibu county, Saitama pref.; Kamiyama, Kamikawa city, Kodama county, Saitama pref.

Makimoto and Takeuchi (1992) Geology of the Yorii District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 136p. (in Japanese with English abstract 6p.)